When galaxies collide, their central black holes tend to spiral toward each other, releasing gravitational waves in their cosmic dance. To explore this uncharted area of gravitational wave science, researchers look a natural experiment in the sky called a pulsar timing array. Pulsars are dense remnants of dead stars that regularly emit beams of radio waves, which is why some call them "cosmic lighthouses."
Mount Wilson is the site where some of the key discoveries about our galaxy and universe were made in the early 20th century. But there is a far lesser known, 100-year-old discovery from Mount Wilson -- one that was unidentified and unappreciated until recently: the first evidence of exoplanets.